There is increasing evidence that beta carotene supplementation is efficacious as a chemopreventive agent for lung cancer. As a first step in this research, a pilot study to evaluate the methodology for a possible national lung cancer prevention clinical trial was undertaken in September, 1984. Our original goals had been to evaluate various recruitment strategies, to obtain baseline distribution for a variety of measurements on the participants and to evaluate the distribution and determinants of response to beta carotene supplementation. To date, we have made substantial progress in the evaluation of these goals. Nearly 400 men have been recruited for the study with few dropouts suffered past randomization. We have determined the yields from the various sources of recruitment, with the highest yields achieved from listings of former or current smokers (MRFIT). Overall, the yields are low (in the range of 1- 5%), but few losses occur after randomization. Our request of continued funding is centered on the need to complete total recruitment of the 400 men and obtain complete data (minimum of one year on drug) on these participants. This last aspect is particularly important because while overall we have observed a substantial response to beta carotene supplementation, there are subsets of participants who have not experienced significant increases in serum carotene levels. These preliminary data are based on the responses observed in 300 men after only 2-4 months of supplementation. Clearly, longer followup is needed to confirm these initial results and to identify the determinants of response/nonresponse. Over the course of this study, we have developed important links with the various occupational groups/unions as well as prominent cancer researchers nationwide. We believe that given additional funding, definitive results will be obtained on the feasibility of conducting a multi-institutional clinical trial using beta carotene supplementation to prevent lung cancer.